Document processing devices include printers, copiers, scanners and e-mail gateways. More recently, devices employing two or more of these functions are found in office environments. These devices are referred to as multifunction peripherals (MFPs) or multifunction devices (MFDs). As used herein, MFP means any of the forgoing.
An electrostatic process unit (EPU) in many toner-based printers and multifunction peripherals performs the printing function. The EPU typically comprises a photoconductive drum, and a developer roller, and can include a charge unit, a toner hopper, a semiconductor laser and developer, among other components as would be known in the art. The EPU can be configured as a field replaceable unit or can be part of a self-contained compact cartridge that includes the toner. Using magnetic and electrostatic forces, the developer roller and the photoconductive drum transfer toner from a toner hopper to a sheet of paper where it is fused by heat to the paper. After the photoconductive drum transfers toner to the paper, a cleaner blade in the EPU removes residual toner and paper dust from the photoconductive drum.
EPUs are disposed inside printers and can become hot during normal operation, both due to the EPU operation itself and due to the operations of other components inside the printer chassis. Excessive heat inside an EPU can degrade the toner present in the EPU. Heat also increases stresses on EPU components which shortens the useful lifespan of EPUs and increases the frequency of maintenance that is required to maintain printers in an operational state.